Late Friday evening, the TSA identified the slain officer as Gerardo I. Hernandez, 39, the first officer killed in the line of duty in the agency's 12-year history. TSA Administrator John Pistole said in a message to employees Friday evening that "no words can explain the horror that we experienced today."

The gunman was wounded in a shootout with airport police and taken into custody, authorities said. His condition was not disclosed.

U.S. law enforcement officials confirmed to CBS News correspondent Bob Orr that the suspect has been identified as Paul Ciancia, 23, of Pennsville, N.J. Officials said he also spent some time in the Los Angeles area.

A preliminary review of government terror databases and watchlists found no connections to Ciancia, and he does not have a significant police record, Orr reported.

CBS News correspondent John Miller reported that according to investigators, Ciancia had a gun in his bag. Inside the bag, investigators came up with notes saying that the TSA were fascists and pigs, anti-American rantings, anti-TSA rantings and references to the new world order, which is another growing conspiracy group that believes the world is going to be taken over by forces and black helicopters and so on.

The officer who was killed was one of the behavioral detection officers that are stationed throughout the airport, looking for suspicious behavior, said J. David Cox Sr., national president of the American Federation of Government Employees.

Initially, Cox said at least three other TSA officers were wounded. Their conditions were not disclosed. Later in the day, the TSA said two other officers were injured.

The Los Angeles Fire Department revised its total number of victims taken to the hospital from six to five, saying one had been double counted. Those numbers included the gunman, the slain TSA officer and one person who broke their ankle.

Airport Police Chief Patrick Gannon said during the news conference that the gunman pulled an assault rifle out of a bag and began to open fire inside the terminal at 9:20 a.m.

"He proceeded up into the screening area, where TSA screeners are, and continued shooting," Gannon said.

A gun is seen on the ground inside Los Angeles International Airport following a shooting Nov. 1, 2013.

@Pascaljosh via Twitter

The gunman went past the checkpoint into the secured area of the airport, Gannon said. Airport Police officers tracked the gunman inside the terminal and eventually engaged with him. He was successfully taken into custody after what Gannon described as an "officer-involved shooting."

"As you can imagine, a large amount of chaos took place during this entire incident," said Gannon. "We believe at this point that there was a lone shooter, that he acted, at least right now, was the only person that was armed in this incident."

Gannon said police completed a security sweep of the entire airport.

The suspect entered the terminal wearing military-like clothing when he opened fire, law enforcement sources told CBS News. Miller reported Friday evening that, according to multiple law enforcement sources, Ciancia had five fully loaded magazines on his person and that ammo was found in a bag nearby. A law enforcement source said "he had enough ammo to kill everyone in that terminal."